Electromagnetic step-by-step mechanism



1,488, 774 G. F. ATWOOD v ELECTROMAGNETIC STEP-BY-STEP MECHANI SM April 1 1924.

Filed Dec. 22. 1922 by MA? Patented Apr. 1, 1924.

UNITED STATES I 1,488,774 PATENT OFFICE.

oEoEeE r. ATWOQD, E NEWARK, NEW JERSEY, assmnon 'ro WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW Y0R-K, 1V.'v Y., A COBIORATION' OF NEW YORK.

ELEcraomeNE'rm s-rEr-EY-srEr MECHANISM.

Application filed December 22, 1922 Serial no. 608,418.

To" all whom it may concern:

7 Be it known that I, GEORGE F. A'rwoon,a citizen of the United States, residing at Newark, in the county of Essex,'State of New Jersey, have invented certain new. and

useful Improvements in Electromagnetic Step-by-Ste Mechanisms, of which the followlng is a ull, clear, concise, and exact descri tion.

T is invention relates to actuating mechanism employing a pawl and ratchet wheel for effecting step-by-step movement of a switch operating element such as the shaft of a sequence switch or selector used in automatic telephone systems and more particularly it relates to a self-interrupting stepping magnet for advancing a swltch on the back stroke of the magnet armature.

The object is to improve the efficiency and 2 reduce the maintenance cost of such deyices. There are a number of stepping devices known in which the work is done on the back stroke of the armature of the stepping magnet; that is to say, the magnet when ener- 2 gized stores up mechanical ener in a spring which on the opening of the circuit of the magnet does the work of advancing the shaft while the armature is recovering its stroke. In these self-interrupting magnet structures an adjustable make and break contact device is provided to control the energization and deenergization of the ma et at the proper times. This contact devlce is adjusted to provide a long closure 85 of contact to permit the magnet to build up its field to the proper strength and before the end of the stroke is reached this contact must be opened to prepare for the back.

stroke, but at this instant the pawl has not yet reached the next tooth in the ratchet wheel and so the momentum of the moving parts must be used to throw the pawl theremaining distance to permit the pawl to engage said tooth. However, as soon as the magnet circuit is opened, the retracting spring of the armature comes into play and opposes this further throw, and inasmuch as the moving parts are light and have little inertia, the margin in these devices is rather small. Conversely, since the contact closes again at the beginning of the back or drivingstroke of the armature, the circuit is closed through the magnet and it begins to build; up in opposition to the retractingspring. This means that the spring must in accordance with the invention, the ma spring pressed pawl 2' is provided for holdso constructed that it works faster than the magnetcan build-up its operating strength. TlllS is particularly objectionable when the stepping'magnet has to drive a variable load, such as operating sequence or multi-contact control switches, wherein in certain positions many contact springs are closed and in other positions only .one contact is closed, the amount of friction varying with the number of contacts shifted by the sequence switch and thus varying the load.' p

In accordance with this invention, auxiliary magnetic means is associated with the armature of the magnet whereby the magnet circuit is closed during practically the entire motive stroke of the armature, and adevice is mounted on the magnet structure to open said contacts near the end of the motive stroke so that the magnet may 'deenergize to permit the armature to restore, the said circuit contacts being held open during practically the entire return movement. Referring to the drawings, Fig. 1 is a side elevation of an ap aratus constructed net circuit bein'g diagrammatically indicated, the pawl being illustrated 'in this figure at the end of an actuating stroke; Fig. 2 is a bottom view thereof; Fig. 3 is a partial assembly view of Fig. 1v showing the pawlv nearly at the end of its stroke in the opposite direction and the resilient contact in engage ment' with its adjustable stop; Fig. 4 is a view generally similar to Fig. 3 but showing a pawl at the end of said stroke and the .magnet circuit opened.

The driven member illustrated is in the form of a. ratchet Wheel 1 arranged to he stepped around by a stepping pawl 2. A

ing the ratchet wheel advanced. The pawl 2 is-pivoted to the end of an arm 3 integrally formed with the armature 40f magnet 6 pivotally mounted at the lower end'portion of a U-shaped frame 5 provided for the return path of the magnetic flux of the magnet 6. A spring 7 secured on the end of arm-3 holds the pawl 2 in engagement with the teeth of the ratchet wheel 1. The arm 3 is held in normal position as shown in Fig. 1 by means of a spring 8, one end of which is attached at 9 to said armature and the other end is attached to an adjustable member 10- pivotally arranged on the side of frame 5. This member maybe adjusted by screw 11 mounted on a bracket 12 which is held securely on the frame 5. by screws 13 and 14;. r

the free side of arm 3 is insulatedly mounted the frame 15 of an auxiliary magnet 16. 1 contact 17 secured on the frame 15 normally engages a resilient contact spring 18. This spring together with the oblong bar 19 act as a back stop and are insulatedly arranged on a bracket 20 which is held securely on the frame 5 by means of screws 21 and 22.- On the end of spring 18 there is mounted the armature 23 of the auxiliary magnet 16. The said armature is preferably connected to spring 18 by means of a knuckle joint 24, best seen in 1, so as to permit the armature to adjust itself relative to the pole piece of the auxiliary magnet, and to prevent the undue distortion of the resilient contact spring 18 during the forward stroke of the armature. The armature 2 3 is held against undue rotation by means of a pin 25 which extends into the clearance hole 26 of the spring 18 and hole 27 of the back stop 19.

Ch the end of the U-shaped frame 5 is secured a bracket 28 provided with an adjustable screw 29 which limits the movement of the resilient contact spring 18 at a predetermined position during the motive stroke of the armature a.

In Fig. 1 the stepping pawl 2 is shown in its extreme forward position against stop 30 and the magnet circuit just closed through the engagement of contacts 17 and 18. Upon the closure of these contacts, assuming contact is closed, the motor magnet 6 and auxiliary magnet 16 energize. The parts are so arranged that armature 23 contacts with its magnet 16 practically simultaneously with the closure of contacts 17, 18 andthereby both magnets 6 and 16 are energized practically at,the same moment. The auxiliary magnet 16 holds armature 23 in contact with its polar face and flexes the resilient spring 18 to maintain this spring in engagement with spring 17 nearly throughout the travel of the main armature 4, now being attracted by the main magnet 6; that is to say, until the device assumes the position illustrated by Fig. 3, which shows the pawl nearly at the end of the motive stroke of the magnet armature, at which time spring 18 is arrested in its movement by stop 29 which mechanically detaches the small armature 23 from its magnet pole face, whereupon the tension in the fiat spring 18' restores said spring to normal position, thereby causing the opening of the circuitthrough both magnets at point 18, 17. The main armature 4 is then retracted by the spiral spring 8 nearly to the limit of its stroke before contacts 17, 18 are again closed, and the cycle repeated. .When spring 8 retracts the armameagre true 4; it operates the ratchet wheel 1 one step and the stepping will similarly be continued as long as contact 4C0 remains closed.

From the foregoing it is apparent that the device of this invention provides a ver efficient arrangement for insuring the ful forward and backward strokes of the ste ping magnet armature and consequently t e proper stepping of the switch, and provides a device which having wide margin allows of low maintenance cost since it requires fewer and non-critical adjustments.

lVhat is claimed is:

1. In a stepping mechanism, a motor magnet, an armature responsive to the energization of said magnet, a pair of contacts in the circuit of said magnet, another magnet cooperating with said contacts for maintaining said circuit closed during sub stantially the entire motive stroke of said armature.

2. In a step-by-step mechanism, a motor magnet, an armature responsive to the energizat-ion of said motor magnet, an auxiliary magnet, and a pair of contacts controlled thereby for governing the forward stroke of the motor magnet armature.

3. In a step-by-step driving mechanism, a motor magnet, an armature responsive to the energization of said magnet, another magnet movableby said armature for controlling the make and break contacts of said motor magnet during the motive stroke .of its armature.

a. In astepping mechanism, a motor magnet, an armature responsive to the energization of said-magnet, a driving pawl carried by said armature, a. ratchet member in operable relation with said pawl, a contact carried by said armature, another contact normally in engagement with the first men tioned contact, and magnetic Jneans. for holding said contacts in engagement during substantially the entire motive stroke of said armature.

5. In a step-by-step mechanism, the combination with a ratchet member, of a motor magnet, an armature associated"therewith,

a pawl carried thereby for operatively engaging said member, a contact carried by said armature, a resilient contact adapted to contact intermittently with the first mentioned contact, an auxiliary magnet carried for operatively engagin said member, an auxiliary magnet carri'eg by said armature, another armature carried by one of said contacts and responsive to the ener ization of the second mentioned magnet, an means for opening said contacts at a predetermined position of said first armature to cause the deenergization of said motor maguctl 7. In a step-by-step. mechanism, the combination with a ratchet member, of a motor magnet, an armature, a pawl carried thereby for operatively engagin said member, an auxiliary magnet carrie by said armature, a pair of normally closed contacts arranged in the circuit of said magnets, and means whereby said auxiliary magnet when ener ize'd is eli'ecti've to maintain'the electrica circuit established during practically the entire motive stroke of said armature. v i

8. In a stepping mechanism, a motor magnet, an armature associated with said magnet, a pair of normally closed contacts in the circuit of said magnet, separate magnetic means for maintaining said contacts closed during the working stroke of said armature, means for breaking said contacts near the end of said stroke to cause the deenergization of said magnet,-and means to retract said armature to normal to close saidcontacts near the end of its retracting stroke. a

9. In, a stepping mechanism, a motor magnet, an armature responsive to the energization of said magnet, a contact carried by said armature, a spring normally engaging said first mentioned contact, magnetic means for maintaining said contacts in engagement during the forward stroke of said armature, means for opening said contact near the end of said stroke, and means for retracting said armature to reestablish contact near the conclusion of its return stroke.

10. In a stepping mechanism, a motor magnet, a frame for said magnet, an arma ture pivotally mounted on said frame, a pair of contacts for controlling the energization of said motor magnet, another magnet in the circuit of the first mentioned magnet and adapted to hold said contacts in engagement during the forward stroke of said armature, an adjustable stop for one of said contacts to cause the opening of said circuit to efiect the deenergization of said magnets.

11. In a stepping mechanism, a plurality of electromagnets, armatures therefor, a pair of contacts actuated by said electromagnets, and a stop for one of said contacts adapted to break the electrical circuit of said magnets during the forward stroke of one of said armatures.

12. In a stepping mechanism, a pair of electromagnets, an armature responsive to the energization of one of said magnets, a resilieiit contact operated by the other of said magnets, means for arresting the movement of said resilient contact during the for contacts, an abutment against which said flat spring engages at the end of the stroke of the motor magnet armature to disengage said flat spring from said contact, whereupon it restores to its normal position and opens said circuit, and a spring for thereupon restoring said motor magnet armature and causing said pawl to advance said ratchet wheel, said armature at the end of its restoring movement bringin its contact again into enga ement with sai fiat spring.

In witness w ereof, I hereunto subscribe my name this 21st day of December,

A. D. 1922. i

GEORGE ,F. ATWOOD. 

